Failure of alpha-melanocyte stimulating hormone to attenuate cerebral complications in experimental pneumococcal meningitis

Alpha-melanocyte-stimulating hormone (alpha-MSH) is an endogenous neuroimmunomodulatory peptide that can inhibit a broad range of inflammatory mediators known to be involved in the pathophysiology of bacterial meningitis. We evaluated the effect of alpha-MSH in a rat model of pneumococcal meningitis. Rats were intracisternally infected with Streptococcus pneumoniae and treatment was started 6 h after infection. Both systemic and intracisternal alpha-MSH failed to influence blood-brain barrier disruption, increased intracranial pressure, brain cytokine concentrations (IL-1beta, IL-6, TNF-alpha, MIP-2, and IL-10), CSF bacterial titers, and clinical parameters of disease severity (weight loss, body temperature, and blood pressure), although the treatment strongly increased the CNS concentrations of alpha-MSH. However, systemic but not intracisternal alpha-MSH slightly reduced the CNS leukocyte accumulation, indicating that leukocyte extravasation is inhibited by alpha-MSH from the blood side. Our results show that alpha-MSH reduces the CNS leukocyte accumulation by its systemic action, but does not attenuate meningitis-associated intracranial complications.     

Induced hypothermia in experimental pneumococcal meningitis.

Pneumococcal meningitis resulting from Streptococcus pneumoniae has a death rate of 28% in adults. In severe head injury and stroke, inflammatory changes and intracranial hypertension are improved by induced hypothermia, which also is neuroprotective. We hypothesized that moderate hypothermia ameliorates inflammatory changes in experimental pneumococcal meningitis. Wistar rats were cooled systemically, and meningitis was induced by pneumococcal cell wall components. The increase of regional cerebral blood flow in the meningitis animals was blocked by hypothermia at 6 hours. The reduction of intracranial pressure correlated with temperature. The influx of leukocytes into the cerebrospinal fluid and levels of tumor necrosis factor alpha in the cerebrospinal fluid were decreased. Cooling the animals 2 hours after meningitis induction to 30.5 degrees C was also protective. We conclude that hypothermia is a new adjuvant approach to reduce meningitis-induced changes, in particular intracranial pressure, in the early phase of the disease.     

Antioxidants attenuate microvascular changes in the early phase of experimental pneumococcal meningitis in rats.

BACKGROUND AND PURPOSE: We tested in a rat meningitis model 1) whether pneumococcal cell wall components are capable of producing changes in regional cerebral blood flow, brain water content, and intracranial pressure similar to those we have already observed after intracisternal inoculation of live pneumococci and 2) whether antioxidants would modulate these alterations in the early phase of meningitis. METHODS: Regional cerebral blood flow as measured by laser Doppler flowmetry and intracranial pressure were monitored continuously for 4 hours after intracisternal challenge. Brain edema formation was assessed by brain water content determinations. We investigated the following groups: rats challenged intracisternally with the whole intact pneumococcal cell wall (n = 7) or the pneumococcal cell wall hydrolyzed by the M1-muramidase (n = 7); rats injected intracisternally with phosphate-buffered saline (n = 6); rats pretreated intravenously with superoxide dismutase conjugated with polyethylene glycol (10,000 units/kg) and injected intracisternally with cell wall components (n = 5) or phosphate-buffered saline (n = 6); rats injected intracisternally with phosphate-buffered saline and pretreated intravenously with polyethylene glycol (10% solution, 1.2 ml/kg, n = 5) or continuously treated with intravenous free superoxide dismutase (22,000 units/kg per hour, n = 6); and rats continuously treated intravenously with deferoxamine mesylate (10 mg/kg per hour) and injected intracisternally with cell wall components (n = 6) or phosphate-buffered saline (n = 7). RESULTS: Both pneumococcal cell wall preparations produced a significant increase in regional cerebral blood flow, intracranial pressure, and brain water content. Conjugated superoxide dismutase as well as deferoxamine prevented the increase in intracranial pressure and brain water content. In addition, the increase in regional cerebral blood flow as observed in untreated, cell wall-challenged rats (baseline, 100%; 183.1 +/- 12.3% after 4 hours, mean +/- SEM) was significantly attenuated by administration of both conjugated superoxide dismutase (136.6 +/- 14.1%) and deferoxamine (149.8 +/- 8.2%) (p < 0.05). Polyethylene glycol-conjugated superoxide dismutase alone produced an increase in regional cerebral blood flow (125.6 +/- 8.7% after 4 hours). We found that polyethylene glycol per se accounts for this action. CONCLUSIONS: These data show that pneumococcal cell wall components containing teichoic acid produce changes in regional cerebral blood flow, intracranial pressure, and brain water content and that oxygen radicals contribute to these pathophysiological alterations in the early phase of experimental pneumococcal meningitis.     

Microvascular changes during the early phase of experimental bacterial meningitis

We investigated the temporal profile of the changes in regional CBF (rCBF) and intracranial pressure (ICP) during the early phase of pneumococcal meningitis in the rat. rCBF, as measured by laser-Doppler flowmetry, and ICP were continuously monitored during 6 h post infection (p.i.). Brain edema formation was assessed by brain water content determinations. Meningitis was induced by intracisternal injection of 75 microliters of 10(7) colony-forming units/ml pneumococci (n = 7). In control animals (n = 6), saline was injected. There was no change in the rCBF or ICP of controls throughout the experiment. However, there was a dramatic increase in rCBF and ICP associated with brain edema formation in untreated meningitis animals. rCBF increased to 135.3 +/- 33.8% (mean +/- SD) in the untreated animals at 1 h p.i. and reached 211.1 +/- 40.5% at 6 h p.i. (p less than 0.05 compared with controls). ICP increased from 2.9 +/- 1.4 to 10.4 +/- 4.7 mm Hg at 6 h p.i. (p less than 0.05 compared with controls). Brain water content was significantly elevated (79.69 +/- 0.24 compared with 78.94 +/- 0.16% in the control group, p less than 0.05). We investigated the effect of dexamethasone (3 mg/kg i.p.), which was given prior to the induction of meningitis (n = 3) or at 2 h after pneumococcal injection (n = 5), indomethacin (10 mg/kg i.v., n = 5), and superoxide dismutase (SOD; 132,000 U/kg i.v. per 6 h, n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)     

Brain Levels of neuropeptide Y in experimental pneumococcal meningitis

Neuropeptide Y (NPY), which is found in high concentrations in several regions of the brain including nuclei of the brain stem and in nerve fibers surrounding cerebral vessels, has been proposed to play a role in regulating cerebral blood flow (CBF) and systemic vegetative functions. Since CBF is altered during meningitis, we examined whether NPY concentrations changed in various regions of the rabbit brain in response to experimental pneumococcal meningitis. Changes were most pronounced in the medulla, where NPY concentration increased threefold after 48 h of infection. Concomitantly, there was an increase in NPY immunoreactive fibers surrounding small vessels in the dorsolateral medulla, especially in the nucleus tractus solitarius. These results suggest that NPY may play a role in inducing some of the hemodynamic changes seen during pneumococcal meningitis.     

Matrix metalloproteinases increase very early during experimental focal cerebral ischemia.

Microvascular integrity is lost during focal cerebral ischemia. The degradation of the basal lamina and extracellular matrix are, in part, responsible for the loss of vascular integrity. Matrix metalloproteinases (MMPs) may play a primary role in basal lamina degradation. By using a sensitive modification of gelatin zymography, the authors investigated the activity of MMP-2 and MMP-9 in frozen 10-microm sections of ischemic and nonischemic basal ganglia and plasma samples of 27 non-human primates after middle cerebral artery occlusion/reperfusion (MCAO/R) for various periods. The gelatinolytic activities were compared with parallel cell dUTP incorporation in the ischemic zones of adjacent sections. In the brain, the integrated density of MMP-2 increased significantly by 1 hour after MCAO and was persistently elevated thereafter. Matrix metalloproteinase-2 expression was highly correlated with the extent of neuron injury and the number of injured neurons (r = 0.9763, SE = 0.004, 2P < 0.0008). Matrix metalloproteinase-9 expression only was significantly increased in subjects with hemorrhagic transformation. In plasma, only MMP-9 increased transiently at 2 hours of MCAO. These findings highlight the early potential role of MMP-2 in the degradation of basal lamina leading to neuronal injury, and an association of MMP-9 with hemorrhagic transformation after focal cerebral ischemia.     

Bradycardia due to hydrogen peroxide irrigation during craniotomy for craniopharyngioma.

Complications of hydrogen peroxide have been described in the literature and typically involve the effects of O(2) emboli. We report a 15-year-old male patient undergoing right frontal craniotomy and excision of craniopharyngioma. A sudden bradycardia occurred after instillation of hydrogen peroxide solution at the surgical site. Stimulation of the anterior hypothalamus after removal of the tumor and hydrogen peroxide irrigation may have triggered intense parasympathetic activity leading to bradycardia. The other possible causes for the complication are discussed.     

Bacterial meningitis as an etiology of perinatal cerebral infarction

Despite significant improvement in mortality rate, survivors of neonatal bacterial meningitis experience a significant incidence of neurodevelopmental sequelae. Neuropathologic studies have demonstrated vasculitis, arachnoiditis, and ventriculitis with secondary edema and encephalomalacia. Areas of cerebral infarction, most commonly thought to be venous in origin, have been reported as well. We performed cranial computed tomographic scans on all eight neonates with bacterial meningitis admitted to our Newborn Special Care Unit within the past 36 months and demonstrated abnormalities in seven. Six of these infants were found to have large areas of infarction related primarily to major arterial vascular distributions. We suggest computed tomographic studies for all neonates with bacterial meningitis and subsequent scans at 4-6 months of age in those with abnormal neonatal scans in order to plan better for early intervention services.     

Developmental events during the early stages of cerebral cortical neurogenesis in man

Summary The telencephalic vesicles of early human embryos and fetuses ranging from 6–18 weeks of ovulation age were subjected to correlative light and electron microscopic, immunocytochemical and Golgi analysis. The cellular events that take place during the early stages of cortical neurogenesis are characterized by the early maturation of layer I. The deployment of radial glia, the formation of the glia limitans, the establishment of the pial-glial barrier, and the migration and maturation of Cajal-Retzius cells within the marginal zone (MZ) all take place by 6–7 weeks. Neurons destined to populate the cortical plate (CP) arrive within the MZ by 7–8 weeks of age and appear to divide the MZ into two layers. Progressive compaction of CP neurons and widening of the intermediate zone characterize the next stage. It is suggested that the early establishment of the pial-glial barrier and the early maturation of the layer I are critical to the subsequent growth and development of the CP.Abbreviations CP Cortical plate - CR Cajal-Retzius - EM electron microscopy - GFAP glial fibrillary acidic protein - GL glial limitans - IZ intermediate zone - ML molecular layer - MZ marginal zone - NSE neuron-specific enolase - SVZ subventricular zone - VZ ventricular zone Supported in part by USPHS grant no. ES 02928. Presented at the 62nd annual meeting of the American Association of Neuropathologists, Minneapolis, 1986     

Cushing's triad in pneumococcal meningitis due to brainstem ischemia: early detection by diffusion-weighted MRI

An infant with pneumococcal meningitis developed signs of raised intracranial pressure during the progression of the disease, including loss of consciousness, hypertension, bradycardia, and respiratory depression. However, both the emergency computed tomography scan findings and intracranial pressure measured by lumbar puncture were normal. Diffusion-weighted magnetic resonance imaging identified multiple lesions with restricted diffusion suggestive of ischemia in the brainstem, explaining the signs observed in the patient. These lesions could not be identified on T(2)-weighted images at that time.     

A case of acute cerebral gas embolism due to ingestion of hydrogen peroxide

Journal of Neurology -     

Morphological study in the early stages of complement C5a fragment-induced experimental meningitis: activation of macrophages and astrocytes

Subarachnoidal application of the complement C5a fragment was used to induce acute experimental meningitis in rabbits and rats within 30–60 min. The early stages of the cellular inflammatory response were studied by means of flow cytometry, transmission electron microscopy and immunofluorescence microscopy. Infiltration of polymorphonuclear leukocytes (PMN) into the subarachnoidal space was the earliest event of the inflammatory reaction. By morphological criteria we found that PMN interacted with cells of the mononuclear-macrophage lineage (MML) and the marginal astrocytes via pseudopodia, whereas the pial cells were not involved in early stages of the inflammatory response. The number of invaded MML that were positive with the ED2 marker increased, indicating the hematogenous origin of the immigrating cell population. PMN were found to infiltrate the perivascular space of the marginal arterial vessel segments. This perivascular infiltration was assumed to be the first manifestation of cerebral vasculitis. The intimate association of resident cerebral cells (astrocytes) with invading PMN and MML is suggestive of a transient interaction of these cell types.     

Gene and protein expression of galectin-3 and galectin-9 in experimental pneumococcal meningitis

Inflammation of the subarachnoid and ventricular space contributes to the development of brain damage i.e. cortical necrosis and hippocampal apoptosis in pneumococcal meningitis (PM). Galectin-3 and -9 are known pro-inflammatory mediators and regulators of apoptosis. Here, the gene and protein expression profile for both galectins was assessed in the disease progression of PM. The mRNA of Lgals3 and Lgals9 increased continuously in the cortex and in the hippocampus from 22 h to 44 h after infection. At 44 h after infection, mRNA levels of Lgals9 in the hippocampus were 7-fold and those of Lgals3 were 30-fold higher than in uninfected controls (P<0.01). Galectin-9 protein did not change, but galectin-3 significantly increased in cortex and hippocampus with the duration of PM. Galectin-3 was localized to polymorphonuclear neutrophils, microglia, monocytes and macrophages, suggesting an involvement of galectin-3 in the neuroinflammatory processes leading to brain damage in PM.     

Reactive nitrogen species contribute to blood-labyrinth barrier disruption in suppurative labyrinthitis complicating experimental pneumococcal meningitis in the rat

Sensorineural hearing damage is a frequent complication of bacterial meningitis, affecting as many as 30% of survivors of pneumococcal meningitis. There is a substantial body of evidence that oxidants, such as reactive nitrogen species (RNS), are central mediators of brain damage in experimental bacterial meningitis. In the present study, we investigated whether RNS also contribute to the pathophysiology of suppurative labyrinthitis in our well-established rat model of pneumococcal meningitis. In all infected rats, but not in uninfected controls, we observed suppurative labyrinthitis. Cochlear inflammation was accompanied by severe blood-labyrinth barrier (BLB) disruption as evidenced by increased Evans Blue extravasation. Furthermore, increased cochlear expression of endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) was detected by immunohistochemistry. Colocalization of iNOS and tyrosine nitration (a marker of RNS attack) indicated that nitric oxide (NO) produced by iNOS contributes to oxidative cochlear damage through the action of RNS. To determine the pathophysiological role of RNS in BLB disruption, rats were treated with peroxynitrite scavengers (MnTBAP and uric acid, UA). Six h after adjunctive treatment with 300 mg/kg i.p. UA or 15 mg/kg i.p. MnTBAP+100 mg/kg i.p. ceftriaxone, BLB disruption was significantly reduced compared with that in infected animals treated only with ceftriaxone. Therefore, we conclude that RNS are involved in the breaching of the BLB during meningogenic pneumococcal labyrinthitis.     

Neuroprotective effects of brain-derived neurotrophic factor (BDNF) on hearing in experimental pneumococcal meningitis

Bacterial meningitis is still one of the most common causes of acquired profound sensorineural deafness in children despite antibiotic treatment. We investigated the neuroprotective effects of brain-derived neurotrophic factor on hearing function in experimental bacterial meningitis. We implanted stainless steel tubes into both cerebral ventricles of Sprague-Dawley rats aged 21 days. Bacterial meningitis was induced by inoculating a strain of serotype III Streptococcus pneumoniae into the cisterna magna. Six micrograms per day of brain-derived neurotrophic factor (groups 1 and 3) or albumin (groups 2 and 4) was injected into the cerebral ventricles 24 hours after or before infection, respectively, for a duration of 7 days. Additionally, all rats received antibiotic subcutaneous treatment starting 24 hours after infection for 7 days. Brainstem auditory evoked potentials were recorded 24 hours before and 24 hours after infection and after 7 days of treatment with brain-derived neurotrophic factor or placebo and antibiotics, respectively, to determine hearing threshold. Our results showed that the hearing thresholds of animals in each group increased significantly 24 hours after infection compared with the results recorded 24 hours before infection (P < .01). After 7 days of treatment with brain-derived neurotrophic factor, brainstem auditory evoked potential responses recurred in 16 ears when stimulated at 75 dB hearing level in groups 1 and 3. Their hearing thresholds significantly decreased compared with the control group 2 (P < .05) and group 4 (P < .01). However, 13 of 14 ears absent brainstem auditory evoked potential responses could still not be identified at 75 dB hearing level in control groups 2 and 4. The improvement of the hearing thresholds in group 3 (treated before infection) was greater than that of group 1 (treated after infection) (P < .05), but there was no significant difference found between the control groups before and after infection (P > .05). Our study supports the hypothesis that the administration of exogenous brain-derived neurotrophic factor can be effective in preventing or treating hearing loss following bacterial meningitis.     

Hearing loss and cochlear damage in experimental pneumococcal meningitis, with special reference to the role of neutrophil granulocytes

Hearing loss is a well-known sequelae from meningitis, affecting up to 25% of survivors. However, the principal components of the infectious and inflammatory reaction responsible for the sensorineural hearing loss remain to be identified. The present study aimed to investigate the impact of an augmented neutrophil response on the development of hearing loss and cochlear damage in a model of experimental pneumococcal meningitis in rats. Hearing loss and cochlear damage were assessed by distortion product oto-acoustic emissions (DPOAE), auditory brainstem response (ABR) and histopathology in rats treated with ceftriaxone 28 h after infection. Rats were treated with Granulocyte Colony Stimulating Factor (G-CSF) initiated prior to infection, 28 h after infection or with ceftriaxone only. Rats were followed for 7 days, and assessment of hearing was performed before infection and 24 h and day 8 after infection. Pretreatment with G-CSF increased hearing loss 24 h after infection and on day 8 compared to untreated rats (Mann-Whitney, P = 0.012 and P = 0.013 respectively). The increased sensorineural hearing loss at day 8 was associated with significantly decreased spiral ganglion cell counts (P = 0.0006), increased damage to the organ of Corti (P = 0.007), increased areas of inflammatory infiltrates (P = 0.02) and increased white blood cell (WBC) counts in cerebrospinal fluid on day 8 after infection (P = 0.0084). Initiation of G-CSF 28 h after infection did not significantly affect hearing loss or cochlear pathology compared to controls. In conclusion, the inflammatory host reaction contributes significantly to the development of hearing loss in experimental meningitis.     

Lack of endothelial nitric oxide synthase aggravates murine pneumococcal meningitis.

Nitric oxide (NO) plays a central role in the pathogenesis of bacterial meningitis. However, the role of NO produced by endothelial NO synthase (eNOS) in meningitis is still unclear. We investigated the influence of eNOS depletion on the inflammatory host response, intracranial complications, and outcome in experimental pneumococcal meningitis. Leukocyte accumulation in the cerebrospinal fluid was more pronounced in infected eNOS-deficient mice than in infected wild type mice. This effect could be attributed to an increased expression of P-selectin, macrophage inflammatory protein-2, keratinocyte-derived cytokine, and interleukin (IL)-1beta in the brain of infected eNOS-deficient mice. However, no differences in the cerebral expression of intercellular adhesion molecule-1, tumor necrosis factor-alpha, and IL-6 as well as of neuronal NOS and inducible NOS could be detected between infected wild type and mutant mice. In addition to enhanced leukocyte infiltration into the CSF, meningitis-associated intracranial complications including blood-brain barrier disruption and the rise in intracranial pressure were significantly augmented in infected eNOS-deficient mice. The aggravation of intracranial complications was paralleled by a worsening of the disease, as evidenced by a more pronounced hypothermia, an enhanced weight reduction, and an increased death rate. The current data indicate that eNOS deficiency is detrimental in bacterial meningitis. This effect seems to be related to an increased expression of (certain) cytokines/chemokines and adhesion molecules; thus leading to increased meningeal inflammation and, subsequently, to aggravated intracranial complications.     

Patterns of cerebral glucose metabolism in early and late stages of Rasmussen's syndrome.

Rasmussen's syndrome is a chronic encephalitis characterized by intractable focal epilepsy and progressive neurologic deterioration with lateralized brain destruction. In the early stages of the disease, the diagnosis can be difficult to make, and brain biopsy is often performed. We evaluated the patterns of cerebral glucose metabolism using 2-deoxy-2-[18F]-fluoro-D-glucose positron emission tomography (PET) in 15 children (age range 2.9-15.4 years, mean age 8.7 +/- 4.3 years) with Rasmussen's syndrome. In 6 patients evaluated early (< or = 1 year of onset of seizures), the PET scan showed areas of abnormal metabolism restricted mostly to the frontal and temporal regions, whereas the posterior cortex was preserved. Pathologic changes seen in the resected cortex were more pronounced in cortical areas of abnormal metabolism than in regions showing normal metabolism. In 9 patients evaluated later (>1 year after onset of seizures), the PET scan showed more diffuse hemispheric metabolic abnormalities including the occipital cortex, but the abnormalities remained highly lateralized. These patterns of glucose metabolic abnormalities in the early and late stages of the disease may facilitate the diagnosis of Rasmussen's syndrome and assist guidance of biopsy in early cases, when structural neuroimaging is still normal.     

Experimental pneumococcal meningitis. Effects of neuraminidase and other pneumococcal constituents on cerebrospinal fluid in the intact dog.

The intracisternal administration of a Type I pneumococcus to mongrel dogs resulted in spinal fluid abnormalities and clinical course and outcome similar to those of meningitis in humans. In order to define the pathogenic role of pneumococcal neuraminidase and other pneumococcal extracts in experimental meningitis, the following preparations were derived from the same Type I pneumococcus: crude neuraminidase, partially purified neuraminidase, heat-inactivated crude neuraminidase, and heat-killed pneumococci. These preparations were administered intracisternally daily for 5 days to a series of mongrel dogs. These substances did not produce clinical morbity similar to that observed in infected animals, even though there was significant decrease in the NANA content of cortical brain subcellular structures in the neuraminidase-treated dogs. It was concluded that the substances investigated were not responsible for morbidity and mortality in experimental pneumococcal meningitis. Both heat-killed pneumococci and the crude neuraminidase preparation elicited significant alterations in spinal fluid glucose and protein concentrations which were similar to those recorded in infected animals; however these abnormalities were not associated with significant morbidity. It is proposed that spinal fluid glucose and protein abnormalities may not be directly linked to brain damage or dysfunction in this experimental model, or in man.